div class=trans-pagebuttonPage 1button div class=trans-image a href=https:reader042fdocumentsinreader042viewer2022020522575067c21a28ab0f07ad030chtml5page1jpg target=_blank amp-img class=trans-thumb alt=Page 1: Progressive Lightning src=https:reader042fdocumentsinreader042viewer2022020522575067c21a28ab0f07ad030chtml5thumbnails1jpg width=142 height=106 layout=responsive amp-imga divp© 1927 Nature Publishing Grouppdivdiv class=trans-pagebuttonPage 2button div class=trans-image a href=https:reader042fdocumentsinreader042viewer2022020522575067c21a28ab0f07ad030chtml5page2jpg target=_blank amp-img class=trans-thumb alt=Page 2: Progressive Lightning src=https:reader042fdocumentsinreader042viewer2022020522575067c21a28ab0f07ad030chtml5thumbnails2jpg width=142 height=106 layout=responsive amp-imga divp© 1927 Nature Publishing Grouppdiv